Study On Controllable Fabrication And Energy Storage Properties For Novel Hollow Microporous Carbon Nanospheres

Hollow carbon nanospheres (HCNS) is a kind of zero-dimensional carbonnanospheres with the unique hollow core and nano-scale shell thickness.Consequently, high pore volume from hollow core is a special characteristic forHCNS besides the general properties of carbon materials. Benefiting from theseunique structures, HCNS have showed widespread applications in many fields, suchas energy storage, gas adsorption/storage and catalysis. Design and preparation ofHCNS by using the porous polymers as carbon precursors has become one of thehottest research topics mainly owing to the rapid development of our ability to designvarious porous polymer materials. However, the choice of polymers as carbonprecursor is largely restricted because they generally require crosslink structure orthermal-induced crosslinking structure to enable the successful transformation ofhollow structure from polymers to carbon. Thus, it is of great importance to explorethe novel polymer precursors to fine tailor the porous structure of HCNS thattargeting for high-value applications.In this thesis, we proposed a synthesis strategy of HCNS with abundant microporeswithin the shell, by taking polystyrene (PS) as the carbon shell precursor and SiO2nanospheres as the hollow core template. Furthermore, the in-depth structure controlof HCNS and the application in energy storage were studied. The research resultswere shown as follow:(1) SiO2@PS nanospheres was fabricated by adopting emulsion polymerizationtechnology in the presence of SiO2nanospheres as the template. Thenhypercrosslinking reaction was employed to construct three dimensionalnano-network crosslinking structures in the polymeric shell. Consequently, themicropores can be produced within the polymeric shell due to its good rigidity. HCNSshowed abundant micropores within the shell because they are from both the threedimensional nano-network crosslinking structure in the polymeric shell and thecarbonization process.(2) The hypercrosslinking reaction conditions have a significant impact onmicropores structure of HCNS. As the hypercrosslinking reaction time increasing, themicropores structure reached the maximum and then decreased; whereas the reaction time is smaller than2h, the micropores structure disappeared. The more the reactiontime, the higher ability to retain the morphology of HCNS. Based on the surface area(988m2g-1) and porosity(1.36cm3g-1) of HCNS, the optimized carbonizationconditions are as follows:heating rate,5oC/min; carbonization time and temperature,3h and900oC, respectively.(3) The experimental results show that HCNS have excellent electrochemicalperformance, especial at high current density. The capacitance in6M KOH can reach113F g-1at current density of10A g-1. As the anode material of lithium-ion battery,the results show that have good rate performance and cycling performance. Thecapacity is619mAh g-1after50cycles at the current density of0.1A g-1. At last, thethicker shell of SiO2@C lead to the better rate performance and cycling performancewhile the yolk-shell structure of SiO2@C can enhance the cycle stability.